Abstract 2434: The anticancer activity of Japonicone A is mediated by inhibiting NFAT1-MDM2 pathway

Abstract

Abstract NFAT1 plays a crucial role in cancer development and progression and has been suggested as a novel target for cancer therapy. We recently report NFAT1 promotes the expression of the MDM2 oncogene, independent of p53. The present study was designed to elucidate the mechanisms of action for a newly identified NFAT1 inhibitor, Japonicone A (JapA), and demonstrate the value of targeting NFAT1-MDM2 signaling in cancer therapy. JapA was identified as a novel NFAT1 inhibitor from our initial screening of a natural product library. Its effects on NFAT1 expression and stability were analyzed in several human breast cancer cell lines with different genetic background, including MCF-7 (estrogen receptor (ER) positive and p53 wild-type), MCF-7 p53−/− (ER positive and p53 knockout), MDA-MB-231 (triple negative and p53 mutant), and MDA-MB-468 (triple negative and p53 mutant) cell lines. The effects of JapA on NFAT1 expression were also determined in MCF-7 and MDA-MB-231 xenograft tumors in vivo. To further demonstrate the specificity of JapA in targeting NFAT1-MDM2 pathway and the importance of NFAT1-MDM2 inhibition in JapA's anticancer activity, MCF7 NFAT1 overexpression (OE) and knockdown (KD) cell lines, as well as pharmacological activators and inhibitors of NFAT1 signaling were used in this study. Our results indicated that JapA showed a significant, specific inhibition of NFAT1 in breast cancer cells in vitro and in vivo. It induced NFAT1 protein ubiquitination and proteasomal degradation, and inhibited NFAT1 nuclear translocation. JapA also disrupted the binding of NFAT1 to the MDM2 P2 promoter, leading to the inhibition of MDM2 transcription. Furthermore, the inhibition of NFAT1 and the NFAT1-MDM2 signaling are critical for JapA's anticancer activity, as shown in NFAT1 OE and KD cell lines. In conclusion, JapA represents a new class of NFAT1 inhibitor. It exerts its anticancer activity through inhibiting NFAT1 and the NFAT1-MDM2 pathway, providing evidence for the value of NFAT1 as a novel target in developing effective targeted therapy for cancers. (Supported by NIH R01 CA112029, R01 CA121211, and R01 CA186662) Citation Format: Sukesh Voruganti, Jiang-Jiang Qin, Wei Wang, Ruiwen Zhang. The anticancer activity of Japonicone A is mediated by inhibiting NFAT1-MDM2 pathway. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2434. doi:10.1158/1538-7445.AM2015-2434